Elucidating the structures and catalytic properties of metallic nanoparticles

The publications contained within this thesis present the application and development of computational methods for the study of metallic nanoparticles and nanoalloys. Principally these studies are dedicated to their structural characterisation and their interactions with small molecules; vital first steps toward understanding their role in key catalytic processes. Publications have also assessed the applicability of statistical mechanical methods and dispersion corrected DFT to these studies. Palladium-iridium nanoalloys, which are under current investigation for their catalytic properties, are studied extensively using a range of computational methods. Their interactions with hydrogen and benzene are probed in order to better understand their role in tetralin hydroconversion and the preferential oxidation of CO. Structures are revealed to reflect the strongly demixing behaviour of the bulk alloy, with nanosize effects seen in their interactions with hydrogen. The Birmingham Parallel Genetic Algorithm is presented and applied to the direct density functional theory global optimisation of Iridium and both gas-phase and surface supported gold-iridium nanoparticles. The program is shown to be capable of overcoming previous size restrictions while characterising quantum size effects in the iridium and gold-iridium structures. Significant differences are seen between the surface supported and gas-phase gold-iridium structures

Spring 1982 Conference Issue

Turf Clippings (page 3) How the RPAR Process is Working (4) Cellular and Genetic Engineering Techniques Applied Towards the Improvement of Turfgrass (7) Fifty-First Annual Turf Conference and Sixth Industrial Show (10) Natural Versus Artificial Turf--an Economical Alternative (13) Fertility Assay of Sands (17

The validity of the Landau-Zener model for output coupling of Bose condensates

We investigate the validity of the Landau-Zener model in describing the output coupling of Bose condensates from magnetic traps by a chirped radiofrequency field. The predictions of the model are compared with the numerical solutions of the Gross-Pitaevskii equation. We find a dependence on the chirp direction, and also quantify the role of gravitation.Comment: 4 pages, Late

DFT global optimisation of gas-phase and MgO-supported sub-nanometre AuPd clusters

The effect of a MgO support on the structures and energies of Au–Pd clusters is calculated at the DFT level.</p

Global optimization of small bimetallic Pd-Co binary nanoalloy clusters:a genetic algorithm approach at the DFT level

The global optimisation of small bimetallic PdCo binary nanoalloys are systematically investigated using the Birmingham Cluster Genetic Algorithm (BCGA).</p

Casimir Energy for a Spherical Cavity in a Dielectric: Applications to Sonoluminescence

In the final few years of his life, Julian Schwinger proposed that the ``dynamical Casimir effect'' might provide the driving force behind the puzzling phenomenon of sonoluminescence. Motivated by that exciting suggestion, we have computed the static Casimir energy of a spherical cavity in an otherwise uniform material. As expected the result is divergent; yet a plausible finite answer is extracted, in the leading uniform asymptotic approximation. This result agrees with that found using zeta-function regularization. Numerically, we find far too small an energy to account for the large burst of photons seen in sonoluminescence. If the divergent result is retained, it is of the wrong sign to drive the effect. Dispersion does not resolve this contradiction. In the static approximation, the Fresnel drag term is zero; on the mother hand, electrostriction could be comparable to the Casimir term. It is argued that this adiabatic approximation to the dynamical Casimir effect should be quite accurate.Comment: 23 pages, no figures, REVTe